Defence: Can spending on arms be justified?

Many Nato countries spend around half of what the US does and it is clear that defence chiefs in Britain and France are concerned about coping if the Libyan campaign continues.

But is defence spending properly controlled and accounted for and how does it impact the economy of the country concerned?

Having set the ball rolling, Gates' speech has come in for a lot of analysis from defence experts globally.

Here, writing on the New York Times economix blog, Bruce Barlett, a defence adviser to Ronald Reagan and George Bush Senior, brings out some other important numbers when it comes to the political debate about military spending.

He writes: "Because the United States has the world's largest economy, its share of world military spending is outsized, accounting for 43 percent of all the military spending on Earth – six times as much as China, which has the world's second largest military budget and accounts for 7.3 percent of world military spending. Russia accounts for just 3.6 percent.

"With polls showing declining support for the war in Afghanistan and increasing talk in Congress, even among Republicans, about cutting the military budget, it appears certain that the Defense Department is going to be downsized and our foreign military commitments scaled back in coming years."

More generally in this week's Guardian, Simon Jenkins, adopts a very controversial position, writing that military spending means that even democracies go searching for wars.

"There is no strategic defence justification for the US spending 5.5% of its gross domestic product on defence or Britain 2.5%, or for the Nato "target" of 2%."

And he continues – "a bomber is two power stations and a hospital not built. Likewise, each Tomahawk Cameron drops on Tripoli destroys not just a Gaddafi bunker (are there any left?), but a hospital ward and a classroom in Britain."

But does it hurt or help the economy? In the UK the defence industry argues it helps.

Oxford Economics compiled a report earlier this year for defence industry group ADS, which crunched some numbers using a nominal £100m increase.

"Alongside an increase in employment this nominal £100 million investment in the defence industry would also deliver an estimated £230 million of benefits to the domestic economy composed of: